Re: [Pan-users] Articles Pan Can't Read

[Duncan]

Mark S Bilk posted on Wed, 10 Aug 2011 05:14:38 -0700 as excerpted:

> (But KNode has no trouble using Astraweb.  Is there more than one
> protocol for requesting an article from a server?  Will I have to dig
> out Ethereal and spend a week decoding hex in network packets?  Aggh!)

Yes.

Messages can be requested by Message-ID or by per-server/per-group 
message sequence number.  The former is a bit more work to implement in 
the client, but is global -- message-ids are the same no matter which 
server you get them from.  This is the way nzb files work, etc.

The latter is as mentioned per-server/per-group, with the server 
assigning increasing article numbers per group.  This is easiest to track 
in terms of read messages, etc, but because each server and each group on 
the server has its own numbering, if a client tracks a message by message 
sequence number, switching servers means losing track of read-message 
info, etc.  If the read-message tracking isn't reset at the same time and 
the new server has lower numbers, everything will appear already read to 
the client, until its read message tracking for that server is reset.  If 
the new server has higher numbers, everything appears unread, as the 
client just sees a big gap in article sequence numbers.

Pan actually makes use of both.  Read-message-tracking is done via per-
server newsrc standard format file, which uses article sequence numbers.  
However, since pan uses an nzb file for tracking its own task queue as 
well, I believe it actually fetches posts via message-id (tho it may fall-
back to message-sequence-number in some instances, I don't know).  It 
also stores them in cache via message-ID, which helps it manage multiple 
servers downloading at the same time, since if the article is already 
being downloaded in another thread (from the same server or a different 
one), a file by that message-id will already exist in cache so the other 
threads simply skip it.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman